Various low fat, low cholesterol and high fiber diets are being recommended for reducing coronary artery disease risk, yet few studies have evaluated the long-term effects of these diets in women with elevated serum cholesterol levels. This project will evaluate long-term effects of cholesterol-lowering diets in premenopausal women with cholesterol levels above 75th percentile for their group. We have developed four metabolic diets which are based on Phase 2 and Phase 3 of the American Heart Association Diet. Four studies, each 6 months in length, will be conducted to examine lipoprotein and other responses to these diets: 1) AHA Phase 3(20% fat, 100 mg/day cholesterol (C), P:S=2); 2) AHA Phase 2 (30% fat, 200 mg/day C, P:S=1); 3) AHA Phase 2 with P:S increased to 2: 4) AHA Phase 2 + fiber. Studies will be conducted in four consecutive years; one diet will be tested in each study. 24 volunteers will consume a "standard" American diet for one month and then one of the experimental diets for an additional five months. Of primary interest are changes in serum lipids and lipoproteins, platelet function, peroxide load and serum and tissue retinoids, carotenoids and tocopherols; postprandial lipemic and glycemic responses, as well as several measures of physiological well-being, will also be examined. The project is undertaken with the goal of providing sound evidence for dietary recommendations which are being made to the American people.